During operation of medium-voltage switchgear assemblies, heat is produced due to transfer resistances which limits the current carrying capacity in the region of the pole parts. Since the pole parts of the switching device are cast into insulating material, such as an epoxy resin or plastic, the dissipation of heat which can be achieved by convection is limited.
The current carrying capacity is therefore limited by the maximum permissible temperature that can occur without damaging the insulating material.
DE 298 25 094 U1 discloses a pole part of a medium-voltage switching device, in which a vacuum interrupter chamber is introduced into an epoxy resin encapsulation and is open on the base side, i.e. at the bottom. The proportionally largest electrical transfer resistance in the current path is produced for physical reasons substantially at the lower contact, i.e. at the movable contact. The heat produced there can substantially only be dissipated via heat conduction and hardly at all via convection. The insulating material epoxy resin is therefore a poor conductor of heat. Accordingly, it is difficult to dissipate heat that is produced in a medium-voltage switching device.